Many modern livestock handling facilities, especially dairies and feed lots, include a system by which animal wastes are collected. A popular method of collecting waste and cleaning livestock holding areas, such as barn floors, involves flushing the floor with water under pressure. The resulting slurry of water and waste is then directed to a holding tank or lagoon to await further processing. Removal of waste by this process is satisfactory and several forms of apparatus have been utilized for collecting and moving the waste material from the floor surfaces. However, equipment for separating the solids from liquids within the slurry has not been adequately developed, especially to an extent where large volumes of waste are to be handled.
The present Applicant's prior patent, U.S. Pat. No. 4,666,602, very serviceably handles and separates such slurries. The apparatus includes an elongated flume and a chain conveyor arrangement with paddles that move about a circuit within a plane along the perforated bottom surface of the flume. The paddles move about a circuit that is inclined with the flume such that one flight of the paddles moves in an upward direction on one side of the flume, and a return flight of equal length moves downwardly on an opposite side of the flume. A slurry is delivered to this apparatus and is moved about the circuit, in which the liquids separate from the solids and are collected in a drainage area toward the bottom end of the flume. The separated solids are then discharged to a press roll which further dries the separated solids.
The above apparatus operates efficiently, even in large volume conditions. However, it has been found that considerably more separation occurs on the "downside" of the conveyor in which the paddles are moving downwardly along the incline. Conversely, relatively little separation occurs on the upward side. Thus, a significant portion of the chain travel in the upward direction is unused. The conclusion is that the overall length dimension of the separator in the '602 patent is not necessary to the separating process. The problem then becomes how to provide a separator in which the usage of the separation draining screen is most effectively utilized in the minimum amount of space.
U.S. Pat. No. 3,864,255 discloses an inclined conveyor but does not utilize scrapers. The apparatus uses a pre-screen separator and a roller at the vertex of the converging inclined conveyor flight sections. Separation from a slurry occurs upstream of the conveyor through an inclined screen. Significantly separated material then drops on the conveyor belt which moves downwardly to a press roller and subsequently upwardly on an inclined portion of the conveyor to a discharge.
U.S. Pat. No. 3,950,562 to Senior discloses an apparatus for removing ash and inorganic compounds from cattle manure. This device makes use of an inclined conveyor having a series of longitudinally spaced baffles on its working flight that are powered to move toward the upward end of the conveyor. A slurry is discharged onto the working flight of the conveyor so the liquids will cascade over the baffles while the solids are carried upwardly to a discharge end of the conveyor. The separation is therefore attempted along the bottom surface of the moving conveyor flight as the flight moves angularly upward.
U.S. Pat. No. 3,959,135 to Shattock discloses an apparatus for dewatering manure slurries that also makes use of an endless belt dewatering screen. However, a press roll is utilized to "wring" moisture from the solids on the screen. The screen is held substantially horizontal and is moved to bring the solids in the slurry into contact between the two press rolls.
A 1979 East German patent document 1,838,764 discloses a manure separator including an inclined adjustable screen box with a fixed screen along a top surface thereof. A slurry of liquid and manure is delivered to a top edge of the screen and is allowed to run downwardly over the screen surface. A conveyor with flights having outwardly projecting brush bristles is positioned above the screen with its working flight moving in an upward direction to run against the direction of flow and keep the screen clean.
Russian Patent 776628 of 1980 discloses a filtering screen in which a horizontal screen is provided and in which scrapers are moved over the screen surface to squeeze liquid from the solids.
An apparatus somewhat similar to the device used in the Russian reference above is disclosed in U.S. Pat. No. 4,419,239. However, this apparatus makes use of a downwardly inclined screen used with pushing paddles along the surface of the screen to separate excess liquid from solid materials delivered to the screen.
As will be more fully understood below, the present apparatus is distinguishable over the known prior separation apparatus by its inclusion of an extent of separation screen that is inclined from opposed directions so that a manure/liquid slurry may be introduced at a top infeed end of the screen and moved downwardly along an infeed section of the screen. Various relationships are disclosed to maximize separation in a minimum distance. A slurry is first exposed to initial separation along a downwardly oriented section of a drain screen, and is then moved upwardly along a discharge section of the screen for final dewatering. Movement influenced by a paddle conveyor having a working flight powered to move and scrape along the drain screen sections from the infeed end of the trough from its discharge end. In combining the downward infeed and discharge sections of the screen in a single trough, in the relationships disclosed herein, a high degree of separation and dewatering efficiency is obtained without requiring a significant dimension along the path of travel for the slurry to accomplish this result.